A stroke is caused by a blood clot or a burst blood vessel in the brain. Every minute that passes without treatment deprives brain tissue of oxygen, which causes it to die and increases the risk of irreversible brain damage.

Often, stroke symptoms are not recognized, which results in a deadly delay to get a stroke victim to the hospital.

Recent studies show that only about half of the people questioned about stroke symptoms were able to identify them. The symptoms include difficulty speaking; paralysis, especially on one side; sudden weakness; loss of balance or vision, and a sudden, intense headache.

"It's surprisingly poor recognition," says Gene Sung, M.D., assistant professor of neurology at the Keck School of Medicine of USC. "Either they don't recognize it, or they think it is not serious and will get better."

A simple three-part test can help identify if someone is experiencing a stroke and speed up seeking help:

• Ask the person to smile, to look for facial paralysis.
• Ask the person to hold up both arms and keep them raised for 20 seconds, to test for weakness and comprehension.
• Ask the person to repeat a simple sentence, such as "It is sunny today," to check for difficulty speaking.

Failure of any of the three parts means that the person should go to a hospital as soon as possible, even if the symptoms seem to go away.

"New therapies are only effective in the early post-stroke time," Sung says. Many of the drugs need to be used in the first three hours, while other treatments have an eight-hour window.

Strokes are the third-leading cause of death and the primary cause of disabilities in adults in the United States. Unlike other organs, the brain does not have the ability to grow new cells and repair itself.

Sung says, "Widespread use of this test could result in prompt diagnosis and treatment of the stroke and prevent extensive brain damage."